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ENZYMES COENZYME is a small organic molecule that serves as a cofactor in a an organic compound that act as a conjugated enzyme. catalyst for a biochemical reaction; Inorgani...

ENZYMES COENZYME is a small organic molecule that serves as a cofactor in a an organic compound that act as a conjugated enzyme. catalyst for a biochemical reaction; Inorganic ion cofactors include zinc, increases rate of reaction but are not magnesium, manganese, and iron; changed in the process chloride occasionally acts as a cofactor water-soluble, globular proteins METALLO-ENZYMES: FEATURES: - It is bound tightly to the enzyme and a) Enhance reaction rates (pH 7.4 and is not dissociated even after several 37°C). An enzyme catalyzed reaction extensive steps of purification. can be 106 to 1012 times faster than uncatalyzed reaction NOMENCLATURE AND b) Enzymes are very specific. CLASSIFICATION OF ENZYMES SUBSTRATE is the reactant in an STRUCTURE OF ENZYME enzyme-catalyzed reaction; it is the substance upon which the enzyme SIMPLE ENZYME – an enzyme “acts” composed only of protein. CONJUGATED ENZYME – an enzyme that has a nonprotein part in 1) Suffix – ase identifies an enzyme addition to the protein part. (urease, lipase); suffix – in in some names of digestive enzymes (trypsin, chymotrypsin, and pepsin) CONJUGATED ENZYME 2) The type of reaction catalyzed by an APOENZYME - is the protein part of enzyme is often noted with a prefix. a conjugated enzyme (oxidase, hydrolase…) COFACTOR - is the nonprotein part 3) The identity of the substrate is often of a conjugated enzyme noted in addition to the type of reaction. HOLOENZYME - is the biochemically ( glucose oxidase,pyruvate carboxylase, active conjugated enzyme produced and succinate dehydrogenase) from an apoenzyme and a cofactor Apoenzyme + cofactor = holoenzyme - Few enzymes exist in their inactive - Holoenzymes refers to the active enzymes with its nonprotein component, form called proenzymes or zymogens. whereas the enzyme without its - Zymogens become active after prior nonprotein moiety is termed an modification in its structure by certain apoenzyme and is inactive. agents. Many times the active form of - If the nonprotein is a metal ion (Zn2+ enzyme acts on zymogen and catalyzes its conversion into active form – process or Fe2+), it is called a cofactor called autocatalysis If it is a small organic molecule, it is PROPERTIES OF ENZYMES termed as coenzyme. - Coenzymes that only transiently A. ACTIVE SITES associate with the enzyme are called - special pocket or cleft within the cosubstrates. enzyme molecule - contains amino acids side chains that participate in substrate binding and E. REGULATION catalysis - Enzyme activity can be regulated, that is, increased or decreased, so that the B. CATALYTIC EFFICIENCY rate of product formation responds to cellular need. - Highly efficient (103- 108) times faster than uncatalyzed reactions F. LOCATION WITHIN THE CELL - Many enzymes are localized in specific organelles within the cell. Such C. SPECIFICITY compartmentalization serves to isolate - highly specific, interacting only with the reaction substrate or product from one or a few substrates and catalyzing other competing reactions. only one type of chemical reaction D. HOLOENZYMES - some enzymes require molecules other than proteins for enzymatic activity CLASSES OF ENZYMES (BASED 3. HYDROLASE ON THE TYPE OF REACTION) - an enzyme that catalyzes a hydrolysis reaction in which the addition of a water 1. OXIDOREDUCTASE molecule to a bond causes the bond to - requires a coenzyme that is oxidized or break. Hydrolysis are central to the reduced as the substrate is reduced or process of digestion. oxidized. - Lipase digest fatty substrates - Lactate dehydrogenase is an - Protease digest protein substrates oxidoreductase that removes hydrogen atoms from a molecule. - Carbohydrase digest carbohydrate substrate ✓ An organic oxidation reaction is an oxidation that increases the number of 4. LYASE C-O bonds and/or decreases he number - is an enzyme that catalyzes the of C-H bonds. addition of a group to a double bond or ✓ An organic reduction reaction is a the removal of a group to form a double reduction that decreases the number of bond in a manner that does not involve C-O bonds and/or increases the number hydrolysis or oxidation. of C-H bonds. Dehydratase – effects the removal of 2. TRANSFERASE the components of water from a double bond. an enzyme that catalyzes the transfer of a functional group from one molecule to Hydratase – effects the addition of the another. components of water to a double bond. Two subtypes: Transaminase catalyzes the transfer 5. ISOMERASE of an amino group from one molecule to ▪ an enzyme that catalyzes the another. isomerization (rearrangement of atoms) Kinases - catalyze the transfer of a of a substrate in a reaction, converting it phosphate group from adenosine into a molecule isomeric with itself. triphosphate (ATP) to give adenosine ▪ There is only one reactant and one diphosphate (ADP). product in reactions where isomerases are operative. 6. LIGASE Carbohydrases - Hydrolysis of glycosidic bonds in carbohydrates - is an enzyme that catalyzes the bonding together of two molecules into Phosphatases - Hydrolysis of one with the participation of ATP. phosphate-ester bonds MAIN CLASSES AND LYASES SUBCLASSES OF ENZYMES : Dehydratases - Removal of H2O from OXIDOREDUCTASES a substrate Oxidases- Oxidation of a substrate Decarboxylases - Removal of CO2 from a substrate Reductases - Reduction of a substrate Deaminases - Removal of NH3 from a Dehydrogenases - Introduction of substrate double bond (oxidation) by formal removal of two H atoms from a Hydratases - Addition of H2O to a substrate, with one H being accepted by substrate a coenzyme ISOMERASE TRANSFERASES Racemases - Conversion of D-isomer Transaminases - Transfer of an amino to L-isomer or vice versa group between substrate Mutases - Tranfer of a functional group Kinases - Transfer of a phosphate from one position to another in the same group between substrate molecule Ligases - Synthetases Formation of a new bond between two substrates, with HYDROLASES participation of ATP Lipases - Hydrolysis of ester linkages in Carboxylases - Formation of a new lipids bond between substrate and CO2 with Proteases - Hydrolysis of amide linkage participation of ATP. in proteins Nucleases - Hydrolysis of sugar- phosphate ester bonds in nucleic acids